1. Field of the Invention
The present invention relates to an output control method of audio guidance signal in a navigation system adapted to search for a travel route from a current vehicle location to a destination and to guide a user in steering a vehicle to the searched travel route, wherein if a plurality of voice guidance signals to be outputted are generated and conflict with one another, an output order of the plurality of voice guidance signals is controlled.
2. Description of the Related Art
As the number of mobile objects such as cars continuously increases, traffic congestion becomes more critical. Particularly, there is a serious problem in that the rate of increase in the number of vehicles is much higher than the rate at which roads and other infrastructures are being expanded.
As one of the solutions to such traffic congestion, attention has been paid to a navigation system. In such a navigation system, a GPS (Global Positioning System) receiver receives navigation messages transmitted by GPS satellites and a sensor unit is installed in a vehicle to detect travel conditions such as the travel speed and direction of the vehicle. Further, the navigation system determines a current vehicle location based on the received navigation messages and the detected travel conditions of the vehicle, and matches the determined current vehicle location to map data so that the current vehicle location can be displayed on a display unit. Moreover, if there is a target location to be guided, including an intersection, or an access or exit of an interchange of an expressway, an urban highway or the like ahead of a traveling vehicle, a voice guidance signal is outputted so that the vehicle can be guided in view of the travel direction thereof at the corresponding target location to be guided.
Therefore, a vehicle user hereinafter referred to as a user can check a current vehicle location and a shortest route from the current location to a destination using the navigation system. Further, under the guidance of the navigation system, the user can beforehand search for a travel route along which a vehicle travels and be guided by means of video and audio signals to steer the vehicle along the searched travel route, enabling to efficiently use the road systems.
Meanwhile, when a vehicle is guided in traveling by means of a guidance audio signal, there may be a case where while a first to-be-guided target location exists at a position within a predetermined distance ahead of the traveling vehicle and a first guidance audio signal for the first to-be-guided target location is being outputted, a second to-be-guided target location exists at a position within the predetermined distance ahead of the traveling vehicle and a second voice guidance signal for the second to-be-guided target location is to be outputted. In this case, the first and second voice guidance signals conflict with each other.
To solve the problem, a Korean Patent Application No. 2003-1640 (Laid-Open Publication No. 2004-64789) was filed by the present applicant. In the application, if there are a plurality of voice guidance signals to be outputted, the levels of the plurality of the voice guidance signals are controlled and then outputted at a time. That is, according to the prior art, if a second voice guidance signal is to be outputted while a first voice guidance signal is being outputted, the level of the first voice guidance signal that is being currently outputted is lowered and the level of the second voice guidance signal is raised so that a vehicle user can clearly listen to the second voice guidance signal that newly begins to be outputted.
However, the prior art is simply designed to lower the output level of the first voice guidance signal, which is being currently outputted, and to raise the output level of the new second voice guidance signal, irrespective of the priority of a voice guidance signal. Therefore, if the priority of the first voice guidance signal is higher than that of the second voice guidance signal, the vehicle user cannot fully listen to the first voice guidance signal with a higher priority. Accordingly, there are many problems in that the travel of a vehicle cannot be correctly guided and safe driving is greatly obstructed.